This year, to the horror of the children, I have developed a bit of a bridge fetish. Now I don’t mean I have been obsessing about spades and hearts over green felt; nor am I professing a deep interest in cantilevered engineering technology as used in women’s bras (or so a male friend told me, though I remain suspicious of his interest in ladies’ underwear).

No! I am excited about swimming under them.

Rivers are wonderful ethereal things that appear boldly in town centres and then peacefully wend their enchanted way through undiscovered countryside before popping up in an entirely different traffic bottleneck. Yes, I’m exaggerating as the Thames path is hardly an untamed wilderness, but discovering the many twists and turns of the upper reaches has shown me some bits of Oxfordshire I didn’t know existed.

At the beginning of the summer I took up wild swimming and, whenever the children are at bay, meander between grassy banks for a kilometre or two with an eclectic bunch (let’s hope they’re not reading this) in brightly coloured hats. And whenever we pass under a bridge I get terrifically excited because this is the moment that the secret world of the kingfisher and dragonfly collides with the commuting world up above and I can put an accurate cross on my mental map, knowing where I am.

Why is this important to me? I think it’s to do with pinning down these memories for years to come. I’m planning, in my twilight years, to regale the staff providing my assistance with my river exploits as their minibus drives over these bridges.

If I was a physicist I’d be hypothesising about three dimensions of reality overlaid in time and space, though I’m clearly not, because these kinds of theories would never make it into any scientific journal.

So instead I’ll just wax lyrical about the bridges we’ve conquered so far: the Cotswold stone Tadpole Bridge at Buckland Marsh, the historic five-arches at Wallingford, and the A34 road bridge beyond Wolvercote. I even took a late September diversion, something David Walliams omitted to do, and swam beneath Stratford-upon-Avon’s bridge and past the Royal Shakespeare Theatre like a neoprene-clad castaway in a production of Twelfth Night.

I’m hoping that the children’s swimming will come along well enough that they’ll soon be able to join me bridge bagging. I’m also working on the Partner-in-Crime but I think he’s more tempted by a jet-ski. But however much certain landlubbers scoff about waterway swimmers being poor vessel-less sailors, this ugly duckling cheerfully swam past the most miserable boaters on the ironically-named ‘Joie de Vivre’ last week, and was definitely better off with the swans!